It looks like my suspicions were correct, Apple didn’t put the Compatibility Support Module (CSM) into the final firmware for the iMac. If I had to suspect reasons why, it was probably to motivate Microsoft to continue supporting Mac versions of Office, and give them a market for Virtual PC.
Without CSM, the only future OS that’s going to run is Vista, and not until Beta 2 goes GM (EFI support is in the feature set, but the bootloader won’t have it until the last minute… if not later). The good news is that if Vista stays on-track, it should make it out about when MacBook Pros start arriving.
But, that said, Apple is clearly standing in the way of running Windows, Linux, or anything other than Mac OS on a Mac. There is no technical reason CSM cannot be in the firmware, and, Intel has said very publicly all Intel Chipset manufacturers (including Apple) have free access to CSM, and Intel will even custom-build CSM for a developer licensing a chipset.
Contributed by: Christopher Price.
UPDATE:
From the EFI Framework FAQ:
What is the Intel Platform Innovation Framework for EFI?
The Intel Platform Innovation Framework for EFI is new software code that allows BIOS vendors to replace the obsolete PC BIOS. It implements the EFI 1.1 interface. It provides the ability to add new features to the pre-boot environment, such as improved platform manageability, serviceability and recovery and improved administrative interfaces, which previously could not operate in the pre-boot environment. The Framework is a product-strength implementation of EFI that is an all-new firmware implementation for platforms all the way down to silicon. The Intel Platform Innovation Framework for EFI, the name of the product, is now Intel’s recommended implementation of the EFI Specification across all Intel Architectures.
Read more about the EFI Framework in this Intel FAQ.

It looks like my suspicions were correct, Apple didn’t put the Compatibility Support Module (CSM) into the final firmware for the iMac. If I had to suspect reasons why, it was probably to motivate Microsoft to continue supporting Mac versions of Office, and give them a market for Virtual PC.
Without CSM, the only future OS that’s going to run is Vista, and not until Beta 2 goes GM (EFI support is in the feature set, but the bootloader won’t have it until the last minute… if not later). The good news is that if Vista stays on-track, it should make it out about when MacBook Pros start arriving.
But, that said, Apple is clearly standing in the way of running Windows, Linux, or anything other than Mac OS on a Mac. There is no technical reason CSM cannot be in the firmware, and, Intel has said very publicly all Intel Chipset manufacturers (including Apple) have free access to CSM, and Intel will even custom-build CSM for a developer licensing a chipset.
Contributed by: Christopher Price.
UPDATE:
From the EFI Framework FAQ:
What is the Intel Platform Innovation Framework for EFI?
The Intel Platform Innovation Framework for EFI is new software code that allows BIOS vendors to replace the obsolete PC BIOS. It implements the EFI 1.1 interface. It provides the ability to add new features to the pre-boot environment, such as improved platform manageability, serviceability and recovery and improved administrative interfaces, which previously could not operate in the pre-boot environment. The Framework is a product-strength implementation of EFI that is an all-new firmware implementation for platforms all the way down to silicon. The Intel Platform Innovation Framework for EFI, the name of the product, is now Intel’s recommended implementation of the EFI Specification across all Intel Architectures.
Read more about the EFI Framework in this Intel FAQ.